The invention relates to cast iron modifiers and method of their application in ferrous metal production, in particular for foundry.
Widely known in the art are cast iron modifiers used to reduce the formation of cementite on the surface of thin-walled cast iron castings.
Known in the art is a cast iron modifier disclosed in Japanese Pat. No. 48-43007 containing, in % by weight, rare-earth metals from 15 to 30, calcium from 10 to 20, aluminium from 5 to 7, and silicon--the balance.
However, the graphitization capacity which is determined by the rate of the formation of cementite on the surface of a production wedge-shaped sample does not enable the production of cast iron castings with a wall thickness from 5 to 10 mm without formation of cementite on the casting surface when casting in metal moulds.
A layer of white cast iron on the surface of a casting exhibits low mechanical properties so that such castings should be subjected to a high-temperature annealing in thermal furnaces to improve quality and ductility of castings.
High-temperature annealing is associated with considerable energy requirements so that the need to provide a modifier for cast iron which would permit castings to be produced with formation of cementite on the casting surface is urgent.
The provision of such cast iron modifier is, however, associated with a number of problems, while known modifiers and their application methods do not bring any solution to the problem.
High-temperature annealing of castings used heretofore after casting in metal moulds results in impaired physical and mechanical properties of castings as a result of formation of ferrite or ferrite/pearlite structure of cast iron. The absence of cast iron modifiers which would make it possible to manufacture thin-walled castings without formation of cementite on the surface of parts does not allow the reduction of power requirements, elimination of the employment of annealing furnaces, auxiliary equipments and operating staff.